Also related are Ahmad ibn Fadlan's writings, a 10th century traveler from Baghdad who described the Varangians, Swedish vikings who traveled to modern-day Ukraine and Russia, who also ended up in the Byzantine army (or something like that, see https://en.wikipedia.org/wiki/Varangians). Eaters of the Dead, a book by Michael Crighton combines those writings plus the story of Beowulf into a book, which was later turned into a film, The 13th Warrior.